A solenoid valve is an electromechanical device for converting electrical energy into magnetic energy. The solenoid valves are found in many application areas. For complying with diverse requirements of different application areas, the manufacturers of the solenoid valves have produced various solenoid valves of different sizes.
FIG. 1 is a schematic perspective view illustrating a conventional solenoid valve. As shown in FIG. 1, the conventional solenoid valve 1 comprises a valve body 10, a valve spindle 11 and a spring 12. The valve body 10 comprises a magnetic coil 101 and a recess 102. The magnetic coil 101 encloses the valve body 10. A recess sidewall 1021 is perpendicular to a recess bottom 1022. The valve spindle 11 is partially inserted into the recess 102 of the valve body 10, so that the valve spindle 11 could be toward the recess bottom 1022 along the recess sidewall 1021. In addition, the valve spindle 11 has a tip part 111 and a protruding edge 112. The tip part 111 and the protruding edge 112 are respectively disposed at two opposite ends of the valve spindle 11. The spring 12 is partially sheathed around the valve spindle 11 and contacted with the protruding edge 112 and the valve body 10. An example of the spring 12 is a helical spring.
Please refer to FIG. 1 again. When a current flows through the magnetic coil 101, electrical energy is converted into magnetic energy by the magnetic coil 101, and thus the valve body 10 is magnetized. As such, a magnetic force is generated by the valve body 10. Due to the magnetic force, the valve spindle 11 is magnetically attracted and moved toward the recess bottom 1022 along the recess sidewall 1021. As the valve spindle 11 is moved toward the recess bottom 1022, the protruding edge 112 is sustained against the spring 12 so as to compress the spring 12. Eventually, the tip part 111 of the valve spindle 11 will collide with the recess bottom 1022. On the other hand, when no current flows through the magnetic coil 101, the valve body 10 is not magnetized and the magnetic force is lost. Since the force offered to compress the spring 12 is eliminated, the compressed spring 12 will be restored. The restoring force of the spring 12 causes the valve spindle 11 to return to its original position where the valve body 10 has not been magnetized. In other words, the valve spindle 11 is moved in a direction distant from the recess bottom 1022.
According to the above-mentioned reciprocating motion of the valve spindle 11, electrical energy is converted into magnetic energy by the solenoid valve 1. During operation of the solenoid valve 1, the tip part 111 of the valve spindle 11 collides with the recess bottom 1022, and thus noise is caused by the collision between the valve spindle 11 and the recess bottom 1022. Due to the configuration of the solenoid valve 1, the noise is usually amplified into low-frequency noise. The low-frequency noise is very sensitive to the human beings. The low-frequency noise is not pleasing to the ears even if the sound volume of the low-frequency noise is very small. In other words, the noise caused by the collision between the valve spindle II and the recess bottom 1022 is unfavorable to most users.